Since at least as early as 1960, covers have been designed for ponds, swimming pools, and the like to collect solar radiation to heat water. The heated water could be used simply to heat swimming pools to a comfortable temperature, or for generation of power, or other industrial uses. U.S. Pat. No. 3,072,920 to Yellot (1963) discloses a swimming pool cover for collecting solar heat. U.S. Pat. No. 3,620,206 to Harris, Jr. et al (1971) discloses a cover over a liquid reservoir for collecting solar energy which can be used for swimming pools or various industrial purposes.
It has been known since at least 1930 that the difference in temperature of sea water at the surface and greater depths is a source of virtually unlimited energy. U.S. Pat. No. 2,006,985, issued Jul. 2, 1935, to Claude, et al, and the article entitled "Power from the Tropical Seas" (by G. Claude in Mechanical Engineering, Vol. 52; No. 12; Dec. 1930) describe a plant for producing electrical energy by using surface sea water at a temperature of about 27.degree. C. and deep sea water at a temperature of about 13.degree. C. The article states that efficiency increases as the square of the difference of temperatures. An article in Solar Energy, Vol. 48, No.s 2, pp. 69-78, 1992 by Schaefer, et al, states that the potential thermal energy from deep fresh water reservoirs could be enhanced by a floating honeycomb pond cover. Thus, the efficiency of the Claude plant could be increased by using a covered solar pond which heats the sea surface water to near its boiling point. However, a covered pond will not produce practical amounts of power unless the pond extends over a large area, and the pond cover can withstand the tropical storms which occur in locations well suited for developing energy from the difference between temperature of sea water at the surface and at lower depths.
U.S. Pat. No. 3,928,145 to Othmer (1975) describes improvements over the original Claude process by using sea water that has been heated with solar radiation. Othmer refers to a temperature difference between cold and warm waters to be as great as 70.degree. C. by flowing water through ponds with black bottoms and transparent covers.
U.S. Pat. Nos. 4,110,174 (1978) and 4,121,997 (1978) to Carson disclose improvements to the processes of Claude and Othmer. The Carson improvement includes, among other things, exposing warm sea water to radiant solar energy to further increase the working temperature difference.
However, none of the prior art to date has provided large, efficient, and durable pond covers which can withstand tropical Storms so that energy can be commercially extracted from sea water at different temperatures.